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Single Particle Probes of d+Au Collisions in PHENIX

Single Particle Probes of d+Au Collisions in PHENIX. Zvi Citron for PHENIX. Outline. Motivation Improvements in the 2008 RHIC Run data set Using the Forward and Backward Rapidity Detectors in PHENIX

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Single Particle Probes of d+Au Collisions in PHENIX

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  1. Single Particle Probes of d+Au Collisions in PHENIX Zvi Citron for PHENIX

  2. Outline • Motivation • Improvements in the 2008 RHIC Run data set • Using the Forward and Backward Rapidity Detectors in PHENIX • Analysis of the Modification of Mid-Rapidity Yields Conditioned on Forward Rapidity Triggers • Results in d+Au • Conclusions and Future Prospects

  3. Motivation • The d+Au collision system allows investigation of cold nuclear matter effects, and insights into initial state conditions. • 2008 RHIC Run (Run 8) has a factor of ~30 increase in statistics over 2003 RHIC Run (Run 3). • Forward and backward rapidity detectors provide access to different x regions within the Au nucleus and thereby probe the nuclear structure function. • By using the forward rapidity calorimeters in PHENIX (MPCs) to trigger on an event, we can investigate the modification of the mid-rapidity spectra under these trigger conditions to learn about the initial state conditions.

  4. Quality of the Run 8 d+Au Dataset • Factor of ~30 increase in statistics will allow for greatly improved study of 0, , and thus also direct  at mid-rapidity. • These studies are underway and will shed more light on cold nuclear matter effects. Mid rapidity mass spectra show ability to measure both 0 and  at high pT.

  5. See Ondrej Chvala’s poster #210! Expanded Reach in pT Mid-rapidity raw 0 spectra • pT reach extended by ~5 GeV/c with respect to published data (Phys. Rev. Lett. 98, 172302 (2007)) • Much improved statistical precision.

  6. Charged Hadrons at Mid-Rapidity • Run 8 allows better precision in the measurement of the mid-rapidity charged hadron nuclear modification factor. • Black bands represent scale uncertainty

  7. Forward Rapidity Detectors Allow Access to Different x Regions Y3, pT x1 x2 x1 x2 Y4, pT Low x at a large rapidity gap. Note: these formulae do NOT take into account the fragmentation function or kT smearing.

  8. 0/Inclusive Cluster 0/Inclusive Cluster h± h± In the PHENIX Detector d Au SOUTH MPC -3.1>>-3.7 NORTH MPC 3.1<<3.7 Central Arm ||<0.35 • Trigger on forward (or backward) identified 0 or unidentified calorimeter cluster. • Detector acceptances are symmetrized.

  9. reconstruct 0 At E>~17 GeV can no longer distinguish 0 from  Analysis Procedure • Look at events in which a high energy pi0 or inclusive cluster trigger is found in one of the MPCs (3.1<||<3.7) • Inclusive calorimeter clusters for higher energies. • Measure the inclusive central arm per trigger yield of charged hadrons in the sub-samples (||<0.35) • Compare North and South in symmetric p+p system to confirm integrity of the procedure • Compare d going side to Au going side to look for saturation, shadowing

  10. p+p :Symmetric Results in a Symmetric System Raw Counts Raw energy spectra of the North and South MPCs in p+p collisions In a symmetric system there is good agreement in the two.

  11. N triggered mid-rapidity h± S triggered mid-rapidity h± p+p :Symmetric Results in a Symmetric System p p 0/Inclusive Cluster in MPC S 0/Inclusive Cluster in MPC N h± h± In symmetric system forward trigger = backward trigger

  12. d Au <Ncoll> =15.4 0/Inclusive Cluster in MPC N 0/Inclusive Cluster in MPC S h± h± (d going side trigger)/(Au going side trigger) Ratio of d Going Side to Au Going Side Triggered Yields • Most central bin, <Ncoll> =15.4 • 0 Trigger in MPC with 9.1<E<12.7 GeV h±/ h± Shadowing, saturation, or other effects may lead to non unity ratio in mid-rapidity trigger associated spectra.

  13. Centrality Dependence of the Ratio Most Central Semi-Central Semi-Peripheral Most Peripheral 12.7 < E trigger < 16.4 [GeV] 9.1< E trigger < 12.7 5.5 < E trigger < 9.1 (d going side trigger)/(Au going side trigger) pT [GeV/c], ||<0.35 The ratio of d going side to Au going side 0 triggered inclusive mid-rapidity spectra.

  14. (d side triggered)/(Au side triggered) Ratio Trends Inclusive Cluster Trigger 0 Trigger ,3.1<||<3.7 The suppression of the d going side triggered yield relative to the Au going side triggered yield as a function of the trigger energy. (Bands indicate systematic uncertainties from the centrality bias associated with the trigger requirement and possible asymmetries stemming from the higher multiplicity in the Au going side MPC.)

  15. Conclusions and Future Prospects • The 2008 RHIC d+Au run is a fruitful source of information on cold nuclear matter effects. • Further analysis will increase our understanding of d+Au collisions and their implications for initial state effects. “Controlling our control”. • The forward (d going) side triggered mid-rapidity inclusive charged hadron spectra is suppressed compared to the backward (Au going) side triggered sample. • We are thinking about how to understand these results in terms of shadowing/anti-shadowing, saturation. • Future analysis underway to measure IdAu with forward/backward and trigger/associated • See also Jiangyong Jia’s posters (217 & 218) for other interesting d+Au results.

  16. Backups

  17. 0 in MPC South

  18. 0 in MPC North

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